From: Laurent Vivier <[email protected]>, Jeff Dike <[email protected]>, Paolo 'Blaisorblade' Giarrusso <[email protected]>
Adds a new ptrace(2) mode, called PTRACE_SYSEMU (or PTRACE_SYSEMU, this is yet
to decide properly), resembling PTRACE_SYSCALL except that the kernel does not
execute the requested syscall; this is useful for virtual environments, like
UML, which want to run the syscall on their own.
This patch includes some suggestions of Jeff Dike to avoid adding any
instructions to the syscall fast path, plus some other little changes, by
myself, to make it work even when the syscall is executed with SYSENTER (but
I'm unsure about them).
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[email protected]>
---
vanilla-linux-2.6.8.1-paolo/arch/i386/kernel/entry.S | 9 ++++--
vanilla-linux-2.6.8.1-paolo/arch/i386/kernel/ptrace.c | 18 ++++++++++---
vanilla-linux-2.6.8.1-paolo/include/asm-i386/thread_info.h | 4 ++
vanilla-linux-2.6.8.1-paolo/include/linux/ptrace.h | 1
vanilla-linux-2.6.8.1-paolo/kernel/fork.c | 1
5 files changed, 25 insertions(+), 8 deletions(-)
diff -puN arch/i386/kernel/entry.S~host-sysemu-2.6.7-4 arch/i386/kernel/entry.S
--- vanilla-linux-2.6.8.1/arch/i386/kernel/entry.S~host-sysemu-2.6.7-4 2004-09-19 12:03:10.375074144 +0200
+++ vanilla-linux-2.6.8.1-paolo/arch/i386/kernel/entry.S 2004-09-19 12:03:10.409068976 +0200
@@ -258,7 +258,7 @@ sysenter_past_esp:
cmpl $(nr_syscalls), %eax
jae syscall_badsys
- testb $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
+ testb $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
jnz syscall_trace_entry
call *sys_call_table(,%eax,4)
movl %eax,EAX(%esp)
@@ -280,8 +280,8 @@ ENTRY(system_call)
GET_THREAD_INFO(%ebp)
cmpl $(nr_syscalls), %eax
jae syscall_badsys
- # system call tracing in operation
- testb $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
+ # system call tracing in operation / emulation
+ testb $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
jnz syscall_trace_entry
syscall_call:
call *sys_call_table(,%eax,4)
@@ -340,6 +340,9 @@ syscall_trace_entry:
movl %esp, %eax
xorl %edx,%edx
call do_syscall_trace
+ cmpl $0, %eax
+ jne syscall_exit # ret != 0 -> running under PTRACE_SCEMU,
+ # so must skip actual syscall
movl ORIG_EAX(%esp), %eax
cmpl $(nr_syscalls), %eax
jnae syscall_call
diff -puN arch/i386/kernel/ptrace.c~host-sysemu-2.6.7-4 arch/i386/kernel/ptrace.c
--- vanilla-linux-2.6.8.1/arch/i386/kernel/ptrace.c~host-sysemu-2.6.7-4 2004-09-19 12:03:10.377073840 +0200
+++ vanilla-linux-2.6.8.1-paolo/arch/i386/kernel/ptrace.c 2004-09-19 12:03:10.409068976 +0200
@@ -358,6 +358,7 @@ asmlinkage int sys_ptrace(long request,
}
break;
+ case PTRACE_SCEMU: /* continue and replace next syscall */
case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
case PTRACE_CONT: { /* restart after signal. */
long tmp;
@@ -365,6 +366,12 @@ asmlinkage int sys_ptrace(long request,
ret = -EIO;
if ((unsigned long) data > _NSIG)
break;
+ if (request == PTRACE_SCEMU) {
+ set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+ }
+ else {
+ clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+ }
if (request == PTRACE_SYSCALL) {
set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
}
@@ -405,6 +412,7 @@ asmlinkage int sys_ptrace(long request,
ret = -EIO;
if ((unsigned long) data > _NSIG)
break;
+ clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
if ((child->ptrace & PT_DTRACE) == 0) {
/* Spurious delayed TF traps may occur */
@@ -575,7 +583,7 @@ out:
* - triggered by current->work.syscall_trace
*/
__attribute__((regparm(3)))
-void do_syscall_trace(struct pt_regs *regs, int entryexit)
+int do_syscall_trace(struct pt_regs *regs, int entryexit)
{
if (unlikely(current->audit_context)) {
if (!entryexit)
@@ -586,10 +594,10 @@ void do_syscall_trace(struct pt_regs *re
audit_syscall_exit(current, regs->eax);
}
- if (!test_thread_flag(TIF_SYSCALL_TRACE))
- return;
+ if (!test_thread_flag(TIF_SYSCALL_TRACE) && !test_thread_flag(TIF_SYSCALL_EMU))
+ return 0;
if (!(current->ptrace & PT_PTRACED))
- return;
+ return 0;
/* the 0x80 provides a way for the tracing parent to distinguish
between a syscall stop and SIGTRAP delivery */
ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
@@ -604,4 +612,6 @@ void do_syscall_trace(struct pt_regs *re
send_sig(current->exit_code, current, 1);
current->exit_code = 0;
}
+ /* != 0 if nullifying the syscall, 0 if running it normally */
+ return test_thread_flag(TIF_SYSCALL_EMU);
}
diff -puN include/asm-i386/thread_info.h~host-sysemu-2.6.7-4 include/asm-i386/thread_info.h
--- vanilla-linux-2.6.8.1/include/asm-i386/thread_info.h~host-sysemu-2.6.7-4 2004-09-19 12:03:10.377073840 +0200
+++ vanilla-linux-2.6.8.1-paolo/include/asm-i386/thread_info.h 2004-09-19 12:03:10.410068824 +0200
@@ -143,6 +143,7 @@ static inline unsigned long current_stac
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_SINGLESTEP 4 /* restore singlestep on return to user mode */
#define TIF_IRET 5 /* return with iret */
+#define TIF_SYSCALL_EMU 6 /* syscall emulation active */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
@@ -152,12 +153,13 @@ static inline unsigned long current_stac
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
#define _TIF_IRET (1<<TIF_IRET)
+#define _TIF_SYSCALL_EMU (1<<TIF_SYSCALL_EMU)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
/* work to do on interrupt/exception return */
#define _TIF_WORK_MASK \
- (0x0000FFFF & ~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT))
+ (0x0000FFFF & ~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SYSCALL_EMU))
#define _TIF_ALLWORK_MASK 0x0000FFFF /* work to do on any return to u-space */
/*
diff -puN include/linux/ptrace.h~host-sysemu-2.6.7-4 include/linux/ptrace.h
--- vanilla-linux-2.6.8.1/include/linux/ptrace.h~host-sysemu-2.6.7-4 2004-09-19 12:03:10.378073688 +0200
+++ vanilla-linux-2.6.8.1-paolo/include/linux/ptrace.h 2004-09-19 12:03:10.410068824 +0200
@@ -20,6 +20,7 @@
#define PTRACE_DETACH 0x11
#define PTRACE_SYSCALL 24
+#define PTRACE_SCEMU 31
/* 0x4200-0x4300 are reserved for architecture-independent additions. */
#define PTRACE_SETOPTIONS 0x4200
diff -puN kernel/fork.c~host-sysemu-2.6.7-4 kernel/fork.c
--- vanilla-linux-2.6.8.1/kernel/fork.c~host-sysemu-2.6.7-4 2004-09-19 12:03:10.379073536 +0200
+++ vanilla-linux-2.6.8.1-paolo/kernel/fork.c 2004-09-19 12:03:10.410068824 +0200
@@ -1008,6 +1008,7 @@ struct task_struct *copy_process(unsigne
* of CLONE_PTRACE.
*/
clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
+ clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
/* Our parent execution domain becomes current domain
These must match for thread signalling to apply */
_